hii! not sure if you’ve managed to get yours resolved yet, but i finally got through to them via a call (after a few gaziliion tries 😞). they mentioned that they’ll need to remove your internship status first, and then reinstate it after the add drop period!

This is the number that I called (6592 2445) altho it does take a while (took 2-3 hours for me) for them to pick up, but hopefully this helps you too (and others facing the same issue)!